1. Field of the Invention
The present invention relates to a probe stylus for inspecting a semiconductor at a wafer state.
2. Description of the Prior Art
A probe stylus in the prior art is constituted by a single electrically conductive needle. In a high precision inspection of a semiconductor device at a wafer state, a probe styluses for applying force and probe styluses for sensing are connected to pads disposed in a semiconductor. These probe styluses are connected to form a Kelvin connection. In such probe styluses, a cantilever type probe stylus and a perpendicular type probe stylus are known. The cantilever type probe stylus contacts obliquely With a pad disposed in a semiconductor device, and the perpendicular type probe stylus contacts perpendicularly with a pad, at an inspection of a semiconductor.
During an inspection of an I/O of a semiconductor device, for example, a high speed logic element, when an output data of a driver of a tester is inputted into a signal input terminal of a semiconductor, and the output from the output terminal of the semiconductor is received by a comparator of the tester, there is case that a dead band appears. For eliminating such a dead band, it is proposed to use a signal line specialized for transferring the data signal from the output terminal of the tester to the input terminal of the semiconductor and another signal line specialized for transferring the signal from the output terminal of the semiconductor to the comparator of the tester. A dead band means a period in which the tester cannot judge the semiconductor because of a conflict of the signals from the output terminal of the semiconductor and the data signal from the output terminal of the driver of the tester.
Many probe styluses are already known, which allows precise inspection of a semiconductor device at a wafer state, even when a large number of pads are disposed in the semiconductor device. Such probe styluses are disclosed, for example, in Japanese Patent Applications JP-A-5-144895, JP-Utility-Model-A-1-174932, JP-A-Utility-Model-61-104380, JP-A-2-124469 and JP-A-4-288847.
FIG. 62 is a perspective view of a probe stylus disclosed in JP-A-5144895. FIG. 62 shows a state that a probe stylus 201 contacts a pad 204 disposed in a semiconductor. The probe stylus 201 is a so-called cantilever type probe stylus constituted by a first electrically conductive member 202 and a second electrically conductive member 203, which are joined to each other so as to form a branching structure.
FIG. 63 is a cross sectional view of a probe stylus disclosed in JP-Utility-Model-A-1-174932. FIG. 63 shows that a probe stylus 211 contacts with a pad 216 disposed in a semiconductor. The probe stylus 211 is a so-called perpendicular type probe stylus constituted by a first electrically conductive member 212, a second electrically conductive member 203 and an insulating member 214 disposed between the first and second probe stylus. The first and second electrically conductive members 212, 213, have a form of a conventional perpendicular type probe stylus. The first and second electrically conductive members 212, 213 and the insulating member 214 are adhered to each other by an adhesive 215.
FIG. 64 is a cross sectional view of a probe stylus disclosed in JP-Utility-Model-A-61-104380. FIG. 64 shows that a probe stylus 221 contacts a pad disposed in a semiconductor. The probe stylus 221 is a so-called cantilever type probe stylus constituted of a first electrically conductive member 222, a second electrically conductive member 223, and insulating member 224 disposed between and around the first and second electrically conductive members 222, 223. The first electrically conductive member 222 has a form of a conventional cantilever type probe stylus. The second electrically conductive member 223 is thinner than the first electrically conductive member 222. The first and second electrically conductive members 222, 223 are fixed to each other by the insulating member 224 so that they form a single body.
FIG. 65(a) is a side view of a probe stylus disclosed in JP-A-2-124469, FIG. 65(b) is a E1xe2x80x94E1 cross sectional view of FIG. 65(a). The probe stylus 231 is a so-called cantilever type probe stylus constituted of a first electrically conductive member for providing force 232, a second electrically conductive member for sensing 233, and an insulating member 234 disposed between the first and second electrically conductive members 232, 233. The first electrically conductive member for producing force 232 has a form of a conventional cantilever type probe stylus. The outside of the first electrically conductive member 232 is covered with the insulating member 234, and the outside of the insulating member 234, in turn, is covered with the second electrically conductive members 233.
Also, JP-A-4-288847 discloses a similar probe stylus constituted of a first electrically conductive member for providing force 232, which has a form of a conventional cantilever type probe stylus and is covered with an insulating member 234, and a second electrically conductive member for sensing 233, which covers the outside of the insulating member 234.
The probe stylus of the prior art, constituted as a single electrically conductive needle, has following drawbacks. In general, a large number of probe styluses are required for high precision inspection of a semiconductor in a wafer state when a large number of pads is disposed in the semiconductor device. However, the setting of the probe styluses of the prior art onto a probe card is difficult when a large number of pads are disposed in a semiconductor device.
Another drawback is that a probe card tends to warp, when perpendicular type probe styluses contact with the pads disposed in a semiconductor device.
An object of the present invention is to eliminate these drawbacks of the probe stylus of the prior art.
Another object is to propose a probe stylus, which allows precise inspection of a semiconductor at a wafer state, even when a large number of the pads are disposed in a semiconductor device.
Another object is to propose a probe stylus which does not cause a warp of the probe card when the probe styluses contact the pads, even when a large number of pads are disposed in a semiconductor device.
The object is attained by a probe stylus according to claim 1.
In an embodiment the probe stylus of the present invention, the cross section of each of the first and second electrically conductive members perpendicular to their longitudinal direction is a half round.
In another embodiment the probe stylus of the present invention, each of the first and second electrically conductive members has a resilient portion at their tip portion, where the probe stylus contacts with a pad disposed in a semiconductor device.
In another embodiment the probe stylus of the present invention, the first electrically conductive member is covered with the insulating member, and the insulating member is covered with the second electrically conductive member, and the first and second electrically conductive members are electrically connected to each other at their tip portion.
In another embodiment the probe stylus of the present invention, the first electrically conductive member is covered with the insulating member, and the insulating member is covered with the second electrically insulating member, and the first and second electrically conductive members are not electrically connected to each other at their tip portion, but are connected to each other through a pad disposed in a semiconductor device at an inspection of the semiconductor device.
In another embodiment the probe stylus of the present invention, the first electrically conductive member is covered with the insulating member, and the insulating member is covered with the second electrically conductive member, and the first and second electrically conductive members are not electrically connected to each other at their tip portion, but are connected to each other through a pad disposed in a semiconductor device at an inspection of the semiconductor device.